218-8 Permo-Triassic Evaporitic Facies as an Archive of Atmospheric Deposition of Mercury

Abstract:

The Permian–Triassic transition contains the end-Permian mass extinction (EPME), which is the most devastating mass extinction event in Earth’s history. It is hypothesized that repeated eruptions of the Siberian Traps led to the EPME through a cascade of biogeochemical feedbacks that destabilized the environment. Additional Triassic eruptions during the Carnian, Norian, and Rhaetian are also thought to have led to major environmental and biotic crises. Mercury (Hg) concentrations are often used as a proxy to identify large-scale volcanism in the sedimentary record. Mercury enrichments, however, may also be controlled by Earth system feedbacks to volcanic drivers leading to planetary-scale destabilization, including changes in climate, weathering, and the amount of oxygen in aquatic environments (e.g., redox). To assess the impact of depositional environments on the sedimentary Hg cycle, we explore a new sedimentary archive–evaporites–preserved in the Staithes S-20 core, Yorkshire, UK, that spans the uppermost Permian to uppermost Triassic.

These evaporitic deposits represent not only marine deposition but also a record of atmospheric mercury paired with ambient seawater Hg concentrations. Approximately 400 evaporite samples from Staithes S-20 are to be measured for mercury concentrations. A low-resolution preliminary dataset reveals significant Hg and Hg/TOC enrichments in the Anisian and Norian. The preliminary data, however, only contain 15 samples. We expect to observe elevated Hg concentrations as well as Hg/TOC values during intervals associated with volcanism, weathering, wildfires, and major increases in precipitation, all of which can impact atmospheric Hg chemistry. These evaporites offer an environment with fewer processes that can deliver Hg to the basin, thereby helping to understand the links between large-scale volcanic activity and environmental change during this important interval of biological evolution.

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